The electronic packaging technology is a comprehensive and diverse system manufacturing technology including all steps from a semiconductor device to a final finished product. Recently, the technologies in semiconductor are developing into integration of more than million cells, and large number of I/O pins, large size die, dissipation of large amount of heat and high electrical performance in case of a non-memory device. However, the electronic packaging technology for such devices has not followed the rapid development of semiconductor industry.
The electronic packaging technology is an important technology that affects performance, size, price and reliability of final electronic products. The importance of this technology is being emphasized according to the development of electronic products pursuing high electric performance, ultra small size/high density, low power, multi-function, high speed signal processing and permanent reliability.
In line on the trend, the flip chip bonding technology, one of the technologies that connect a chip to a substrate electrically has drawn a lot of attention. However, the flip chip bonding technology involves complex bonding processes utilizing a existing solder comprising coating of solder flux on a substrate, aligning a chip which is formed of a solder bump and a substrate which is formed of a surface electrode, reflowing of a solder bump, removing of remained flux, filling of underfill and hardening. So this technology increases the price of final products.
Therefore, in order to simplify the aforementioned complex process, a packaging technology in a wafer state which coats and processes polymeric material with flux and underfill functions in a wafer state draws attention. In addition a study on a flip chip bonding technology using a conductive adhesive is in progress. The conductive adhesive has advantages of low price compared to a general solder flip chip, possibility of ultrafine electrode pitch, environmentally friendliness due to not using flux or lead components, and processibility at low temperature.
The conductive adhesive can be divided into an anisotropic conductive adhesive (hereinafter referred to ACA) and an isotropic conductive adhesive, and comprises: conductive particles such as Ni, Au/polymer or Ag; and thermosetting, thermoplastic or blend type insulating resin integrating advantages of them. The research on flip chip technology utilizing expensive but environmentally friendly ACA as a connection material has been very active. In order to support the research the development of ACA material and application of ACA flip chip technology have been also very popular.
In addition to the flip chip bonding technology using the conductive adhesive, the technology using NCA that does not have conductive particles is introduced. However, there has been a problem of low reliability for conventional NCA material because it exhibits a large coefficient of thermal expansion and dielectric constant and also has inferior mechanical and electrical features.
As explained above, since it uses solder bump, existing flip chip packaging technology is not only complicated in its assembly process, but also not environmentally friendly. And packaging cost is high due to the cost of ACA material when ACA is used. When NCA is used, reliability of the product is lowered because of large coefficient of thermal expansion and dielectric constant and its inferior mechanical and electrical features. Considering the reality that electronic packaging technology is on the rise as an important field in creating added value of products, it is a very important task to develop environmental friendly flip chip technology that solves the existing problems and can substitute existing solder connection.